[engine_work] I Forgot How Much I Missed It!

[pugdamo 111 2 Cars]

Your telling me you would bend a valve turning it over by hand and not notice,good one.Im sure valve/piston contact would make a noticable sound even though they are small stems.

And no i didnt read your post,was just making a suggestion to try and save someone some work,lets hope if he takes the head off your right.

[Toddy 7]

As Petert says measure lift @ tdc and also measure the full lift of the cams.

 

If these are std gti6 cams then full lift is 9.9mm and tdc should be around .5mm inlet and .7mm exh at tdc.

 

Doof had an issue on his build iirc where due to the seats been recut needed the valve stems to be ground slightly as the valves were being held off the seat which may be your issue.

Edited January 1, 2014 by Toddy

[DrSarty 90 1 Cars]

Thanks for the advice.

 

Addressing a few of the points:

> std GTI6 cams

> crank pulley is standard (with the rubber bush which had slipped), however engine was timed via cambelt fitment using an 8v solid crank pulley with the OE locking hole

> no valve seats were recut; only re-lapped in the valves from whence they came

> during cambelt fitment, I turned the engine over lots of times and encountered no metal-metal resistance

> cam sprockets are now - exhaust = originally fitted, centrally locked 'vernier' cam pulley / inlet = changed originally fitted item (same as exh sprocket) to a Xantia sprocket and hub*

 

*On this last point, which may actually be critical to my issue, I 100% checked that the Xantia hub with its notch for locking would behave exactly the same as the original sprocket with its 'lollipop-type' hub which has a hole; the 2 lined up perfectly.

 

My feeling is that it simply can't be the 180deg out as perhaps incorrectly feared, as all locking holes/notches (crank plus 2 x sprockets) lined up perfectly during cambelt fitment and test engine turns. However, I'm now considering that there must be some misalignment from using the different sprocket, which in combination with cam timing has meant that on each compression stroke, some valves aren't fully closed reducing compression to zero.

 

I haven't heard or felt any type of restriction during my by-hand engine rotations, so I cannot convince myself that any valves are bent.

 

My current plan is:

> remove O/S wheel

> remove cam covers (in & exh)

> rotate by hand the engine such that cams (I mean sprockets & hubs in combination) are in their locking/timed position

> remove the aux belt and crank pulley and check alignment of the crank locking/timing hole - THIS IS PHASE ONE & MAY REVEAL SOMETHING

> following on - if timing seems OK - I will rotate engine by hand to cyl 1 at TDC (now TDC technically exists twice) so I can observe cams rotating, pushing down onto lifters/followers and noting the valve open/close status - SHOULD THERE BE ANY BENT VALVES, I WOULD EXPECT TO SEE SOME DIFFERENCE IN LIFTER BEHAVIOUR (GAP TO CAM LOBE) ON ANY THAT ARE

 

Perhaps stating the obvious (and BTW I did mark TDC on the flywheel and block but can't see those marks now the gearbox is fitted, hence having to find TDC again), one of the TDC positions i.e. the correct one on the compression stroke, should basically have closed or rather very nearly closed valves. In fact I believe exh and inlet will probably be open a small but even amount; as people have mentioned, inlet lift at TDC (on the compression stroke) should be around 0.5mm IN and 0.7mm EX.

 

I am hoping that after the above investigation I should have a clear(er) picture of what's gone on. I would hope to be lucky as per PeterT's story, and that we have no bent valves and just bad timing, meaning a re-time of cams, crank and belt will get everything working nicely. What I will do though is get a pair of OE GTI6 cam sprockets with hubs of the 3-bolt vernier variety, and refit the cambelt using these instead.

 

WANTED (therefore) - 1 matching pair of OE GTI6 cam sprockets with hubs, clearly marked as inlet and exhaust.

Edited January 1, 2014 by DrSarty

[pugdamo 111 2 Cars]

I agree 100% with what you have put,im sure its a timing issue,hopefully as simple as fitting the gti6 cam sprockets should put it right,good luck

[petert 550]

Could you put the engine at TDC (1 and 4) and take a picture of the cam lobes from the cam belt end?

[Paul_13 212 1 Cars]

Both gti6 inlet and exhaust cam sprockets/hubs are identical

[DrSarty 90 1 Cars]

Peter: Yes I can; will post today.

 

Paul: Originally I would've agreed, but now I have a mix of GTI6 exhaust and Xantia (exh I think) on the inlet, and even according to my GTI6 service guide there do appear to be differences. See below:

 

 

Cam ident & refitment:

 

As you know there are 2 types of GTI6 cam sprocket/hub combo - one with a single lock for the hub and sprocket via the main 18mm bolt, and the other locks the hub with the main 18mm bolt, and 3 x 10mm bolts clamp the sprocket to the hub. I have a single-bolt (originally fitted) exh sprocket and hub on the exh i.e. no change, but a Xantia hub and sprocket (possibly exhaust - but it did line up fine) on the inlet.

 

I now much prefer the latter (3-bolt) style, but perhaps my Xantia sprocket on its hub on the inlet cam has got my timing out.

 

I'll get some pics today, but FYI (perhaps again):

> head was assembled following guide (above) showing orientation of camshaft keyways

> guide was followed throughout for cambelt fitment

> Inlet single-bolt locking tang was compared carefully with Xantia hub and appeared to deliver same effect

> No interference/contact was felt when timing up engine

> Cambelt fitting (after a few attempts getting tension right -even with Xantia hub) delivered all locking holes lining up nicely after several/may rotations of the engine by hand

 

Perhaps then the answer lies in the change to the Xantia hub and sprocket. I have now sourced a pair of GTI 3-bolt hubs and sprockets, and I will be swapping over to those soon, hopefully getting a (well-earned) result.

Edited January 2, 2014 by DrSarty

[allye 530 3 Cars]

This is quite odd! From reading through the last couple of pages I really have to agree you would be doing extremely well to bend some valves and not notice when turning it over by hand.

 

Having a shoot in the dark for funsies I would have a guess its this parts bin pulley setup.

[Miles 331 1 Cars]

Was the head vacuum tested at all? this is the only real way of knowing if the valves are shutting, Next step is a leak down test if you can borrow one but you need a compressor for this, it shows you where any issues are

[DrSarty 90 1 Cars]

As you can perhaps imagine, I'm getting massively frustrated with this, as I'm sure I did everything right (regardless of the cam pulley swap).

 

Luckily the weather was dry and quite warm today, and I got on with some serious investigating.

 

1) Based on my previous post, the diagram showing cam hub identification seems to indicate based on the far left groove I have that the Xantia 2.0 16v hub and sprocket I'm using are identical and are for the inlet.

 

2) Moreover, before finding TDC, with the cam hubs in the locking positions, with an easy slide in of an M6 bolt which can be screwed in slightly by hand, inlet, exhaust and crank all align as they're supposed to. I know the crank pulley is correct even with my (slipped) GTI6 crank pulley because I marked the line of the woodruff key, which I know points backwards to a lower cover bolt at about 9 o'clock. THEREFORE, IT WOULD APPEAR THAT CAMS, HUBS, SPROCKETS, CAMBELT TENSION AND TIMING ARE ALL FINE.

 

3) As per the pictures below {a} to {f}, you'll see my TDC locating efforts and cam lobe positions at both TDCs. Now as I mentioned earlier, I believe TDC on an engine with the head on is ONLY at the top of the compression stroke, when all valves are basically closed.

 

 

 

 

 

 

What I'm a little confused about, is that only the second TDC (prior to the beginning of a new cycle, i.e. an induction stroke) appears to show any lift for measurement, even if it's only 0.7mm. So I'm getting very confused and frustrated at how cam lobes which appear as they do in pics {b} and {c} with both valves closed which is what I believe is TDC - with inlet lobe peak at approx. 10.30 and exhaust at approx. 1.30 (i.e. mirroring each other) - could have any lift to be measured. So is my understanding of TDC FUBAR'd?

 

Pics {d} and {e} show 'the other TDC' where both lobes are opening the inlets and exhaust a little but it's difficult to see as they're following the lifters and in a small bath of oil. Only this TDC makes any sense to me for measuring any lift, but this is just at the end of the exhaust stroke getting ready for induction. So which bloody TDC is it? And have I got the timing right?

 

4) Finally, WHAT I HAVE FOUND - after removing the inlet manifold to watch the inlet valves operate - IS THAT THE INLET VALVES NEVER SEEM TO FULLY CLOSE!!! Now if that's true, that's a/the explanation for no compression. I would assume that the exhaust valves are also doing this, BUT WHY?

 

As Miles has hinted, and someone else did earlier ref valves not closing fully, why on earth would this be the case? I didn't have the seats recut, and valves went back from where they came (i.e. all fully numbered and replaced in the same seats). I did however lap all the valves in again, but why on earth would that stop the valves fully closing, as they certainly appeared closed once fitted with the head on the bench?

 

Is it that somehow the fully assembled head, with double-springs, collets, caps, serviced lifters and camshafts bolted down is somehow now not letting the valves close fully, i.e. imposing some kind of upper limit?

 

I'm starting to think now that swapping cam sprockets in the car is not the solution, although it might've been if the Xantia inlet hub/sprocket was unsuitable. BUT....in checking the inlet valves, I noticed that at no point did they appear to close fully! This means the timing is irrelevant IF the valves are never closing.

 

I tested this by rotating the engine until each pair of inlet lifters (one after the other) had the base of each cam lobe on it i.e. the peak/nose of the lobe was on the centre line of the lifter pointing directly away from the valve, i.e. zero lift. For each cylinder, I squeeze a dropper full of oil onto the back of both inlet valves, and voila, after a little time it had seeped past the valve onto the cylinder.

 

So whilst I will fit the GTI6 cam pulleys when they arrive, I'm probably going to have to remove the head and the head fully checked.

 

So simply put, WTF is going on?

Edited January 2, 2014 by DrSarty

[Anthony 1,000]

The valves will only be open at one TDC, namely the end of the exhaust stroke where the exhaust is closing and the inlet opening.

 

The other TDC is the end of the compression stroke and you'd have no compression if the valves were open at that point!

 

You'll need a dial gauge to check valve lift at TDC (and an accurate TDC)

[DrSarty 90 1 Cars]

I agree, and I know I'll have no compression with even partly open valves.

 

The 2 TDCs you've explained is exactly what I said, but I was asking which one was the TDC people refer to for measuring lift. You've said what I concluded, i.e. at the end of the exhaust stroke. That makes sense.

 

What isn't making sense is why everywhere I looked, TDC was referred to as the other one at the end of the compression stroke.

 

But now it's clear, that TDC for measuring valve lift is the one at the end of the exhaust stroke (not the compression stroke which is all I could find).

 

HOWEVER, have you or anyone got any opinion on why not one single inlet valve pair seems to close fully? If it's the old chestnut of bent valves again, then would it really effect ALL of the inlet valves, and when did it happen when turning by hand?

 

Unless there's any other solution, perhaps in the lifters or springs or valve fitment, then I'm forced to conclude that we have 8 bent inlet valves (perhaps exhaust too) which are not allowing the valves to close fully.

 

On that basis, it's head off, give it to a shop, have them strip and inspect and advise.

 

I do have a dial gauge though with magnetic clamp stand, and will attempt to measure lift at (the correct) TDC on inlet and exhaust tomorrow; perhaps this will shed some more light on what's happening.

Edited January 2, 2014 by DrSarty

[pugdamo 111 2 Cars]

I know it may be a ball ache but you could take the cams out just to see that the valves are actually able to close.

[Toddy 7]

You mention 'serviced lifters' were these fitted when you refitted the head?, if so you could change these without lifting the head. Alternatively take one of the inlets out and check the dimensions are what they should be.

 

 

Valves can bend when people rebuild a head and incorrectly place the cams in the wrong positions, therefore to get the cam sprockets in the correct positions they turn one of the cam sprockets to the correct position and unfortunately the valves can clip, bending slightly. This is when a sprocket is turned more than 90ish degrees etc as they never line up perfectly anyway.

Edited January 2, 2014 by Toddy

[DrSarty 90 1 Cars]

Lifters:

All original GTI6 lifters were 'serviced' by soaking in degreaser for 24hrs, then banged out on a wooden board to release the piston and spring assy from the bucket, then soaked again in numbered sets, washed in boiling water and immediately coated in WD40 before reassembly, i.e. spring put into small piston (with ball valve at end) and then that piston pushed inside cylinder, then pair pushed snugly into bucket. The wearing faces of the lifters were fine so weren't resurfaced.

 

All lifters went back into original positions.

 

Cams:

These were fitted as I've mentioned as per the guide, with the woodruff key orientation as shown by '23' and '24' in the diagram in an earlier post on this page. This way they fit flat, and once clamped down need minimal rotation to reach locking positions once the hubs/sprockets are fitted. This minor rotation was done with clear visibility of valve positions, so no valves touched.

 

Head & Cambelt Fitment:

Again, as per the guide, with the head offered to the block with the cams pinned (as well as the crank pinned at midway pistons) and keyway aligned.

 

I am struggling to think of any particular moment when the cams could've been rotated such that any valves got bent; but then again I've been a d*ck once!

 

And Damo: Your advice could be excellent suggesting removing the cams from the head to check valve closure, as if the head's likely coming off anyway, I might as well inspect this element and remove the influence of the cams and lifters. If the valves don't close, then we know some/all must be bent or something else is hindering closure, so I can remove the head. If the valves close, then we know it was the influence of the cams etc preventing closure.

Edited January 2, 2014 by DrSarty

[Paul_13 212 1 Cars]

After I had a head rebuilt, the lifters were pumped more than usual and it took several turns of the cam to release the pressure on the lifters causing the valve to seat .

[Paul_13 212 1 Cars]

http://forum.205gtidrivers.com/index.php?showtopic=132228&page=1

 

Look down towards the bottom of page 1

[petert 550]

I was trying to see if the lobes were "rocking" on #1 exhaust TDC. ie the inlet starting to open and the exhaust almost closed. The pics are inclusive, but it appears from "c", which is #1 compression TDC, that it will be correct. The lobes will be rotated 180deg on the next TDC, meaning the lobes would appear to be laying flat on the bucket. When fitting cams without locking holes, it's normal to start with the cams in the "rocking" or overlap position. Thus I'm just double checking the initial "rough" cam timing position. It would have compression even if out half a tooth either way.

 

Inlet of 0.7mm lift at TDC would be correct for those cams. It's difficult to see & measure, thus you need a dial indicator and an accurate TDC mark.

 

When servicing the lifters, is it possible you put the pistons back together incorrectly? I'm clutching at straws here, as I feel if they were overfilled with oil they would have bled off by now. I agree that cams out is the next step.

[dcc 855]

Rich. Sounds like valves are bent to me. Get a refurb head fitted. Get yours refreshed. Either way get the head off.

[DrSarty 90 1 Cars]

Again, thanks for all the support.

 

Pete: I am fitting cams with sprockets with locking holes just in case you haven't caught that, and they currently still line up perfectly. I will measure lift at TDC, but I'm fairly confident now that timing is not the issue.

 

I'm also pretty confident that my TDC marks are accurate, on the crank pulley and the flywheel and block. I may have given the impression it was a guestimate, but I took an hour of measuring using cylinders 1 and 4, first visually looking for rising-plateau-falling piston marker (dayglo orange pencil), then equal rise and fall either side to mark the midpoint i.e. TDC. It should be suitably accurate.

 

If it is bent valves, then as said, I have no idea when or how it happened, but it will show up IF I need to remove the head, as currently the plan (after TDC measurement) is to remove the cambelt and the cams and see if the valves then seal (by putting petrol down the ports to see if it holds or leaks through). If it doesn't hold, it's head off time. With the cams and lifters out, perhaps the valves will rise and seat properly; I guess they'd stay slightly open if bent (?).

 

When the cams are out, I'll check the lifters, as I must admit, incorrect lifter assembly has crossed my mind as I've wracked my brains thinking of causes.

 

Another possible cause I haven't mention is that the HG is not MLS. Mine came from Lyndale engines for about £15, and was clearly labelled as XU10J4RS. It's £65 cheaper than an MLS, but surely the HG choice is not going to stop the valves closing, as that's dictated by the cams, valve springs and lifters alone? Anyway: I'll have to fit a new HG if I remove the head, so should I definitely fit an £80 MLS HG instead?

 

If somehow I have assembled the lifters incorrectly, but consistently wrong, (what an idiot), then that might explain how perhaps they won't compress enough to allow full closure. Being 'over-pumped' is one thing, but they were fitted evacuated i.e. empty, and the engine's had plenty of spinning on the starter for things to even out.

 

So now I think it's lifters wrong, and failing that bent valves. We'll see once the cams are out. If I can avoid head off I'll be delighted.

 

EDIT:

After a wee Google I found this useful article showing lifter cleaning and reassembly.

http://geometroforum.com/topic/3937058/1/

I've got the strangest (sick to stomach) feeling I've assembled the smaller cylinder that goes inside the piston the wrong way round! It's just a suspicion, but that might explain things. I'd be surprised if I had having done this before, but I may have had a lapse. And let's face it, if it isn't this then it'll have to be mysteriously bent valves.

Edited January 2, 2014 by DrSarty

[welshpug 1,622]

£15 is only £25 less than a standard mls hg Rich, however I've not had issue with good quality ones.

[DrSarty 90 1 Cars]

Not when the quote for an MLS HG was £88 it isn't.

 

Hopefully, if the lifters are the issue, it's cams out, lifter rebuild, cams in, belt on, cam covers on and vroom! (I seriously don't want to remove the head)

[welshpug 1,622]

Quoting from the wrong place rich, victor reinz unit from gsf, or a genuine item from peugeot/citroen is £40.

 

Sod those overpriced things.

 

Valves, if they have been held open then pray it is less than 2.5 mm or so, otherwise they will be bent.

Edited January 2, 2014 by welshpug

[DrSarty 90 1 Cars]

From what I could see down the ports when the lobe positions should've meant closed valves, we are talking 1mm or probably less. Hopefully good news.

 

Logic says though, following this recent idea, that with the cams out - even with the lifters left in - the valves should close fully, testable by fuel poured in the port. Fingers crossed eh!

[Miles 331 1 Cars]

And the aftermarket HG generally have the tab's poking out into the cambelt area as well, If you do take the head off then the OE Pug gasket is the one to use